Concrete Mix Design:
Mix design is a method which determines the proportions of cement, water, fine aggregates and coarse aggregates to produce the concrete of required strength, workability and durability with minimum cost.
Mix design can be divided into following two categories
1. Design mix concrete and 2. Nominal mix concrete.
1. Design Mix Concrete:
When the proportions of concrete ingredients are decided by adopting certain established relationships ( based on assumptions from a lot of experiments) to produce the concrete it is known as design mix concrete.
In design mix concrete, it is assumed that compressive strength of concrete is totally dependent on the water-cement ratio.
2. Nominal Mix Concrete:
When the concrete is produced by taking standard arbitrary proportions of concrete ingredients, it is known as nominal mix concrete. This method is generally used when the quality control requirement for design mixes are difficult to execute. As we have explained for normal work, nominal mix concrete can be designed by taking cement, fine aggregate and coarse aggregate in the ratio of 1 : n : 2n.
Concrete Mix Proportions For Nominal Mix Concrete:
|Grade Of Concrete
||Total quantity of dry aggregates by mass per 50 kg of cement, to be taken as the sum of the individual masses of fine & coarse aggregates (maximum) in kg
||Quantity of water per 50 kg of cement (Maximum) in litres
||Proportion of fine aggregate to coarse aggregate (By mass)
|Generally 1 : 2 but subject to an upper limit of 1 : 11/2 and a lower limit of 1 : 21/2
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